;************************************************************************ ; * ; Filename: L10-ADC_dec-out.asm * ; Date: 1/12/07 * ; File Version: 1.2 * ; * ; Author: David Meiklejohn * ; Company: Gooligum Electronics * ; * ;************************************************************************ ; * ; Architecture: Baseline PIC * ; Processor: 16F506 * ; * ;************************************************************************ ; * ; Files required: none * ; * ;************************************************************************ ; * ; Description: Tutorial 10, exercise 1 * ; * ; Displays ADC output in decimal on 2x7-segment LED display * ; * ; Continuously samples analog input, scales result to 0 - 99 * ; and displays as 2 x dec digits on multiplexed 7-seg displays * ; * ;************************************************************************ ; * ; Pin assignments: * ; AN0 - voltage to be measured (e.g. pot or LDR) * ; RB5, RC0-5 - 7-segment display bus (common cathode) * ; RB4 - tens enable (active high) * ; RB1 - ones enable * ; * ;************************************************************************ list p=16F506 #include radix dec ;***** CONFIGURATION ; ext reset, no code protect, no watchdog, 4MHz int clock __CONFIG _MCLRE_ON & _CP_OFF & _WDT_OFF & _IOSCFS_OFF & _IntRC_OSC_RB4EN ; pin assignments #define TENS_EN PORTB,4 ; tens enable #define ONES_EN PORTB,1 ; ones enable ;***** VARIABLE DEFINITIONS VARS1 UDATA digit res 1 ; digit to be displayed (used by set7seg) adc_out res 1 ; raw ADC output adc_dec res 2 ; scaled ADC output (LE 16 bit, 0-99 in MSB) mpy_cnt res 1 ; multiplier count tens res 1 ; digits of scaled output: tens ones res 1 ; ones ;********************************************************************** RCCAL CODE 0x3FF ; processor reset vector res 1 ; holds movlw with factory RC cal value RESET CODE 0x000 ; effective reset vector movwf OSCCAL ; update OSCCAL with factory cal value pagesel start goto start ; jump to main program ;***** SUBROUTINE VECTORS set7seg ; display digit on 7-segment display pagesel set7seg_R goto set7seg_R ;***** MAIN PROGRAM MAIN CODE start ; initialisation clrw ; configure PORTB and PORTC as all outputs tris PORTB tris PORTC movlw 1< TMR0<2> cycles every 2.048ms) ;***** Main loop main_loop ; sample input bsf ADCON0,GO ; start conversion w_adc btfsc ADCON0,NOT_DONE ; wait until conversion complete goto w_adc movf ADRES,w ; save ADC result banksel adc_out movwf adc_out ; scale to 0-99: adc_dec = adc_out * 100 ; -> MSB of adc_dec = adc+out * 100 / 256 clrf adc_dec ; start with adcdec = 0 clrf adc_dec+1 movlw .8 ; count = 8 movwf mpy_cnt movlw .100 ; multiplicand (100) in W bcf STATUS,C ; and carry clear l_mpy rrf adc_out,f ; right shift multiplier btfsc STATUS,C ; if low-order bit of multiplier was set addwf adc_dec+1,f ; add multiplicand (100) to MSB of result rrf adc_dec+1,f ; right shift result rrf adc_dec,f decfsz mpy_cnt,f ; repeat for all 8 bits goto l_mpy ; extract digits of result movf adc_dec+1,w ; start with scaled result movwf ones ; in ones digit clrf tens ; and tens clear l_bcd movlw .10 ; subtract 10 from ones subwf ones,w btfss STATUS,C ; (finish if < 10) goto end_bcd movwf ones incf tens,f ; increment tens goto l_bcd ; repeat until ones < 10 end_bcd ; display tens digit for 2.048ms w10_hi btfss TMR0,2 ; wait for TMR0<2> to go high goto w10_hi movf tens,w ; output tens digit pagesel set7seg call set7seg pagesel $ bsf TENS_EN ; enable "tens" display w10_lo btfsc TMR0,2 ; wait for TMR<2> to go low goto w10_lo ; display ones digit for 2.048ms w1_hi btfss TMR0,2 ; wait for TMR0<2> to go high goto w1_hi banksel ones ; output ones digit movf ones,w pagesel set7seg call set7seg pagesel $ bsf ONES_EN ; enable ones display w1_lo btfsc TMR0,2 ; wait for TMR<2> to go low goto w1_lo ; repeat forever goto main_loop ;***** LOOKUP TABLES TABLES CODE 0x200 ; locate at beginning of a page ; Lookup pattern for 7 segment display on port B ; RB5 = G get7sB addwf PCL,f retlw b'000000' ; 0 retlw b'000000' ; 1 retlw b'100000' ; 2 retlw b'100000' ; 3 retlw b'100000' ; 4 retlw b'100000' ; 5 retlw b'100000' ; 6 retlw b'000000' ; 7 retlw b'100000' ; 8 retlw b'100000' ; 9 ; Lookup pattern for 7 segment display on port C ; RC5:0 = ABCDEF get7sC addwf PCL,f retlw b'111111' ; 0 retlw b'011000' ; 1 retlw b'110110' ; 2 retlw b'111100' ; 3 retlw b'011001' ; 4 retlw b'101101' ; 5 retlw b'101111' ; 6 retlw b'111000' ; 7 retlw b'111111' ; 8 retlw b'111101' ; 9 ; Display digit passed in W on 7-segment display set7seg_R banksel digit movwf digit ; save digit call get7sB ; lookup pattern for port B movwf PORTB ; then output it movf digit,w ; get digit call get7sC ; then repeat for port C movwf PORTC retlw 0 END